The present invention relates to an ink ribbon device for printers, particularly matrix printers, which include a reciprocating carriage moving along a printing platen and carrying a print head; usually an ink ribbon cartridge is mounted in the frame for the printer, containing an ink ribbon being, for example, held in the cartridge in an endless so-called Moebius loop fashion. A portion of the ribbon extends outwardly from two legs of the cartridge, the legs positioned in-between them, the print head and the platen. Moreover, it is assumed that the ribbon has at least two parallel bands of similar color.
Basically then, these kind of ribbon devices have a ribbon run in a closed loop in order to obtain maximum possible use out of the ribbon, without deterioration of the quality as for as readability of the printed characters are concerned. In case there is just one band, so-to-speak for a single level, the ribbon will be used up fairly rapidly. On the other hand, the ribbon is usually much wider than the height of a character simply for mechanical reasons which amounts to a considerable waste. In this case then, it is of advantage to sub-divide, so-to-speak, the ribbon into two bands. It is therefore necessary to change from one of the bands to the other. If the ribbon is run in a Moebius loop that changeover occurs automatically and does not have to be effected physically, by turning the cartridge over. However, even this approach is not necessarily advantageous because one of the bands always so-to-speak runs along and is not used, while the other portion is being used up but from one side only. It should be realized that the single side concept of a Moebius loop is a mathematical construct. Each band is and continuous to be used from one side only.
The other possibility exists to have a two track or two band ribbon and to subject this ribbon to a wobble motion i.e. to move it up and down so that, in fact, both strips are being used; indeed, that is an added utilization because in a Moebius loop one will use both sides. However, it should be realized that, as a consequence of this wobbling, the ribbon is in fact sinusoidally used and if for some reason there is a "harmonic" relationship between the wobble motion and the ribbon length, there still may be unused ribbon portions, while certain sinusoidal track portions may overlap. This is basically an unforeseeable situation.